Field of the Invention
The present invention is related to determining energy production controls for a given subterranean hydrocarbon (oil) field production and more particularly to specifying controls for sustaining optimal field production (by means of a plateau-like profile over time).
Background Description
Energy production facility designs are normally based on general field production considerations for a given subterranean hydrocarbon (oil) field. Generally, economic business units provide a lower design limit. This limit can based on the plateau production duration and on the length of time required to recover facility construction costs. Plateau production means sustained, constant energy production for the selected production duration. The economic business units also prescribe an upper design limit for the plateau duration, typically set contractually, e.g., a contractual provision limiting production from a given field to a certain time frame, or tied to field concessions. Thus, determining field production typically includes finding production controls (e.g. field rate) that aim at sustaining constant production for a selected production duration.
Previously, designers generated plateau production profiles ad-hoc, through trial and error and guided by prior experience. Designers used simple, analytical oil production models to guesstimate an optimized plateau value. Those guesstimates, however, relied on very simple imprecise models. Those models are not robust, often lead to wrong decisions, and frequently failed to consider inherent uncertainties.
More recently, designers have used simulation-based field production to optimize designs. Considerations on the duration of the plateau (e.g., minimum and maximum duration) provided general optimization constraints to these field simulations for more accurate results. While more accurate, including uncertainty in this simulation-based approach and formulating the problem as a general optimization problem, made arriving at a solution more complex and expensive because of a multivariable optimization problem needs to be solved. Uncertainty in certain parameter (e.g. geometry of the reservoir) is typically quantified by considering a set of parameter distributions, each of them with an associated probability. Arriving at a solution frequently requires thousands of reservoir flow simulations, taking several days of computations to complete. Thus, the associated computing cost may be prohibitive. Moreover, this approach frequently is unsuited for interactive, rapid decision-making.
Thus, there is a need for quickly, inexpensively and methodically generating field production controls that, under quantifiable uncertainty, aim at optimizing sustained production (i.e. by means of a plateau-like profile over time), and, also for generating field production controls for achieving a previously given plateau duration.